1. Field of the Invention
This invention relates to an electrophotographic apparatus having a cleaning device used for an image formation apparatus such as a printing apparatus using an electrophotographic system.
2. Description of the Related Art
In a conventional printing apparatus using an electrophotographic system, a cleaning system using a rubber blade, a fur brush, or the like, has gained wide acceptance for cleaning untransferred residual toner adhering to a photosensitive drum after transfer. A system using a rubber blade and a fur brush in combination has also been employed. Particularly, a fur brush cleaning system has been often used for high speed machines, and the residual toner on the photosensitive drum, which has not been transferred to a recording sheet, is removed by the fur brush.
A cleaning fleece or blade has also been used to clean any contamination which has not been removed by the fur brush.
In the printing apparatus of this kind, a gap producing roller for defining a gap between an exposure portion (using an LED array) for forming an electrostatic latent image and the peripheral surface of the photosensitive drum, and a gap producing roller for defining a gap between the peripheral surface of the photosensitive drum and a sheet entry guide at a transfer portion are arranged to rotate while maintaining contact with the peripheral surface of the photosensitive drum outside the print area.
A film-like toner adheres to the peripheral surface at the end portions of the photosensitive drum, where the gap producing rollers keep contact, due to scattering toner during printing. This portion is also cleaned, with the print area portion of the photosensitive drum, by a combination of the fur brush cleaner with a cleaning fleece or a combination of the fur brush cleaner with a cleaning blade.
In the case of the former combination, i.e. the fur brush cleaner with the cleaning fleece, the cleaning fleece portion corresponding to both end portions of the photosensitive drum, to which the film-like toner adheres, is made coarser than usual so as to improve the cleaning effect, but scratch and wear occur on the peripheral surface of the photosensitive drum. In the case of the latter combination, a push force of the blade can be changed, but flattering and feeding failure of the sheet may occur. Further, the cleaning effect drops at the portion where the amount of the toner is great, such as the gap producing roller contact portions, because adhesion of the toner to the blade is strong.
As described above, since the conventional cleaning system cannot effectively clean the film-like toner adhering to the peripheral surface of the photosensitive drum, with which the gap producing rollers are in contact, the following problems occur.
(1) The original gap cannot be secured. PA1 (2) When a large amount of the toner adheres to the drum, the toner may peel off at the contact portion with the gap producing rollers, may contaminate the peripheral portions, and may exert an adverse influence on printing.